As the next-generation radio communication system for performing a higher speed communication with a higher capacity, as compared with the 3rd-generation and 3.5th-generation radio communication systems operated at present, LTE has been standardized in 3GPP which is the standardization body of a radio communication system. The technical specifications of the LTE have been specified as 3GPP Release 8, and Release 9, which is an upgrade version of Release 8, and LTE Advanced, which is a sophisticated version of the LTE, have been currently considered.
As an uplink transmission power control method in the LTE, for example, the following technology has been proposed (see Non-Patent Document 1). In the technology disclosed in the Non-Patent Document 1, based on the state where overload indicator (OI), which represents interference information indicating the level of interference to a base station in an uplink, is notified between base stations, the transmission power of a radio terminal connected to an own base station is controlled according to the OI.
Furthermore, in the LTE Release 9, a small cell (referred to as a “femto cell”), which is a communication area having a radius of about several meters, is formed, and detailed functions and conditions of a small cell base station (referred to as a “Home eNodeB”), which is a small base station installable in an indoor space, have been standardized. The small cell base station can disperse traffic of a large cell base station (referred to as a “Macro eNodeB”), which forms a large cell (referred to as a “macro cell”) that is a communication area having a radius of about several hundreds of meters, and can cover a dead zone in the large cell.